Mitral Insufficiency (MI) – Trivial or Mild

(also called mitral regurgitation (MR), chronic degenerative valve disease (CVD), myxomatous degeneration or endocardiosis )

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The Normal Heart

Mitral Insufficiency or Mitral Regurgitation

  • DEFINITION (What it is):
    • Mitral insufficiency is due to a degeneration of the mitral valve, which separates the left atrium (the receiving chamber) from the left ventricle (the pumping chamber)
      • The valve starts leaking backwards, so that blood flows both forward and backward within the heart.
        • There are varying amounts of leak
          • This usually (but not always) corresponds to how enlarged the chambers get
        • with a small amount of leak, there are no chamber enlargements.
          • This stage is usually found when a veterinarian hears a murmur with a stethoscope.
    • This is an age related degenerative process, and not related to infection or inflammation
  • EPIDEMIOLOGY (Who gets it):
    • Mitral insufficiency is a disease of small breed dogs, though we see occasional cases in medium and large breed dogs
      • It is very common, seen in about 75% of all canine heart cases
        • about 30% of cases will have degeneration of both the mitral and tricuspid valves
        • about 10% of cases will have only tricuspid valve degeneration (see Tricuspid Insufficiency)
      • These breeds include miniature Poodles, minature Schnauzers, terriers, Dachsunds and American Cocker Spaniels.
      • Cavalier King Charles Spaniels
        • are at increased risk for developing the disease
        • occurs earlier in this breed
    • It occurs in older pets
      • > 5 years
  • It is very rare in cats
  • CAUSE:
    • Mitral insufficiency is due to age-related degeneration of the valve
      • It appears to be related to collagen disorganization at the cellular level
      • It is not related to
        • infection
        • inflammation
        • dental disease (though dental health is important for your pet)
      • There is probably a genetic component since we see this commonly in certain breeds, but these genes have not been identified
  • CLINICAL SIGNS (with trivial or mild mitral insufficiency):
    • A murmur is just turbulence within the heart. See Murmurs
    • There are no signs seen otherwise in the pet
  • DIAGNOSTICS (See Tests We Often Perform)
    • Staging of the mitral valve disease is typically performed with echocardiography (heart ultrasound), and this is typically all that is warranted in these cases.
    • No therapy is generally warranted
    • No dietary changes are necessary
    • No exercise restriction is warranted
    • For the short term, excellent
    • About 1/3 of these pets will progress onward to significant disease
    • We understand that your money has to be spent wisely to be able to monitor and treat your pet for it’s lifetime, so we are very respectful of your finances and yet provide excellent care for your pet
      • We work as a team with your family veterinarian, and maintaining routine and non-specialist care is a very important part of our consideration
    • These cases should be monitored
      • How and how often they should be monitored really seems to vary by the cardiologist or practitioner